This invention relates to a process for the purification of a diolefin hydrocarbon stream containing trace quantities of acetylene and sulfur compounds and the cyclic regeneration of an at least partially spent selective hydrogenation catalyst containing at least one metal. More particularly the present invention relates to methods of reclaiming catalysts which have become deactivated and to the catalytic reduction of acetylenic bonds in the presence of dienes without substantial destruction of the diene compounds.
The selective hydrogenation of the acetylene compounds is generally conducted in the presence of a selective hydrogenation catalyst and hydrogenation and conducted at an elevated pressure and temperature. Such selective hydrogenation catalysts are well known in the art and include, for example, a catalyst containing copper metal associated with one or more activator metals impregnated on an alumina support. During the acetylene hydrogenation, polymers are formed and deposited on the catalyst thereby reducing the activity of the catalyst. One method of regenerating spent or partially spent catalyst is to perform a controlled carbon burn with oxygen and subsequent metal reduction with hydrogen to remove catalyst contaminants which are formed as an undesirable by-product of the acetylene hydrogenation. The carbon burn regeneration technique necessarily requires that the reaction zone contain spent catalyst be taken off line and that ancillary regeneration equipment be provided.
Another alternative technique for regenerating spent or partially spent catalyst is to contact such catalyst with hydrogen and a polymer solvent in order to restore at least a portion of the fresh catalyst activity.
Some of the diolefin hydrocarbon stream containing trace quantities of acetylenes also contain trace quantities of sulfur compounds. These diolefin hydrocarbon feedstocks produce a deactivated catalyst which is not satisfactorily regenerated via the known and conventional regeneration techniques.